Hello students are moving on to the laboratory method in laboratory how do we prepare hydrogen by action of a dilute acid on zinc so how do we go about it the chemicals used for the reactions are granulated zinc dilute hydrochloric acid, dilute  sulfuric acid how do we go about it step one that we are following is take a stand place a flat bottom flask containing zinc renewals  inside it so this is a stand for us we are going to attach our round bottom flask inside of which we are adding granulated zinc why granulated zinc is because zinc granules  are preferred for this reaction rather than pure zinc  because the impurities present in granulated zinc is copper which has a catalyzing effect and speeds up the rate of reaction for that reason zinc renewals are preferred and the second take on the second step what do we do we place 2 hold a rubber cork attach it to the round water flask through one of the whole or we are going to attach a thistle funnel self funded and through the second whole we are going to a attach delivery tube through a rubber cork now we have a tub which is filled with water inside of which we are going to have water inside of which are we are going to add our inverted gas jar which is attached to the Beehive shelf now insert the other end of the delivery tube to the gas jar now since the pattern set up done let’s move ahead how to how to perform the experiment and this is a delivery tube  now through the thistle funnel we are going to pour either diluted HCL it that is hydrochloric acid dilute sulfuric acid through the funnel  not the nitric acid why  because nitric acid being a very strong oxidizing agent oxidizes the hydrogen and converted and into water and we are looking for hydrogen and not for water  that is why we do not make use of nitric acid in the following reaction now the tip of the thistle funnel it should be dipped it HCl  properly why so as to prevent the gas from escaping through the thistle  funnel that is that is completely immersed in the acid now when the reaction takes place a between Zinc renewals and dilute  Hcl it leads to formation of hydrogen gas and these hydrogen gases they pass through the delivery tube reaction will gradually start in the form of effervescence now what do we mean by effervescence these are rapidly forming bubbles which our colors  effervescence now these effervescence which are of hydrogen gas it is collected by the downward displacement of water Because it is virtually insoluble  in water what does hydrogen gas the hydrogen gas that is form  it is insoluble in water and if you collect it over the air what happens is it forms an explosive mixture with air that is what we do not collect it in air why  we are collecting it over water and cannot be collected by downward displacement of air that is why we are collecting it right on the displacement of water the reaction that inside apparatus  the about just is zinc when it comes in contact with hcl it you get zinc chloride which is that ZnCl2 along with that hydrogen gas likewise if you make use of zinc Along with sulfuric acid that is dilute H2So4 you get zinc sulfate that isZnSo4 along with that there is a release of hydrogen gas so it’s arrow  reaction need not be balance that is a second reaction Why  because it’s a self  balanced chemical reaction now impurities which are present in hydrogen can be now where do these impurities arise from granulated zinc being in impure on treatment with dilute hcl4 or a dilute  sulfuric acid  evolves  in traces gaseous impurities what are those gaseous impurities will look at them and these impurities we further removed by passage of the impure gas through the three washer bottles and a UTube but first let us understand those impurities those impurities are Arsine which is Ash3 then you can also have phosphine  impurities that is PH3 we can also have hydrogen sulfide that is H2S impurities  it can also be Sulphure  dioxide  SO2 can also be carbon dioxide co2 can also be oxides of nitrogen that is NO,NO2 or N2O and can also be water vapour in the form of impurities.